Table 1. Expected grain yield due to various planting dates and final plant populations.

Planting
Date

Plant population (final) per acre

10,000

12,000

14,000

16,000

18,000

20,000

22,000

24,000

26,000

28,000

30,000

32,000

34,000

36,000

Percent of optimum yield

10-Apr

62

68

73

78

82

85

88

91

92

93

94

94

93

91

15-Apr

65

71

76

81

85

88

91

94

95

96

97

96

96

94

20-Apr

67

73

78

83

87

90

93

96

97

98

99

98

98

96

25-Apr

68

74

79

84

88

92

94

97

98

99

100

100

99

97

30-Apr

68

74

79

84

88

92

95

97

99

100

100

100

99

97

5-May

67

73

79

83

87

91

94

96

98

99

99

99

98

97

10-May

65

71

77

82

86

89

92

94

96

97

97

97

96

95

15-May

63

69

74

79

83

87

89

92

93

94

95

95

94

92

20-May

59

65

71

75

80

83

86

88

90

91

91

91

90

89

25-May

55

61

66

71

75

79

81

84

85

86

87

87

86

84

30-May

49

55

61

65

70

73

76

78

80

81

81

81

80

79

4-Jun

43

49

54

59

63

67

70

72

74

75

75

75

74

73

9-Jun

36

42

47

52

56

60

62

65

66

67

68

68

67

65

Source: Nafziger. 1994. J. Prod. Ag 7:59-62. Yield response to planting date extrapolated beyond May 25 with concurrence of author.
Note: The highlighted area represents the optimum ranges (98 to 100% yield) of plant populations and planting dates for productivity levels greater than about 125 bushels per acre. Optimum plant populations for soils with historical yields less than about 100 bushels per acre will likely not respond to final plant populations greater than about 24,000 plants per acre (R.L. Nielsen, Purdue Agronomy).